Third-Order Magnetic Susceptibility of an Ideal Fermi Gas

At low temperature and under weak magnetic field, non-interacting Fermi gases reveal both Pauli paramagnetism and Landau diamagnetism, and the magnitude of the diamagnetic susceptibility is 1/3 of that of the paramagnetic one. When the temperature is finite and the magnetic field is also finite, we demonstrate that the paramagnetism and diamagnetism start to deviate from the ratio 1/3. For understanding the magnetic properties of an ideal Fermi gas at quite low temperature and under quite weak magnetic field, we work out explicitly the third-order magnetic susceptibility in three cases, from intrinsic spin, orbital motion and in total. An interesting property is in third-order magnetic susceptibilities:when viewing individually, they are both diamagnetic, but in total it is paramagnetic.     

Electronic transport in quasicrystals

Mobility of electrons in quasicrystals is considered in the framework of the fractional Fermi surface (FS) model, i.e., a multiconnected FS with many electron-hole pockets. The Mott law for the variable range hopping conductivity is obtained when intervalley scattering processes with small momentum transfer are taken into account. The transition to the power-law temperature dependence is discussed.     

Head-on collision of ion-acoustic solitary waves in a Thomas-Fermi plasma containing degenerate electrons and positrons

Head-on collision between two ion acoustic solitary waves in a Thomas-Fermi plasma containing degenerate electrons and positrons is investigated using the extended Poincaré-Lighthill-Kuo (PLK) method. The results show that the phase shifts due to the collision are strongly dependent on the positron-to-electron number density ratio, the electron-to-positron Fermi temperature ratio and the ion-to-electron Fermi temperature ratio. The present study might be helpful to understand the excitation of nonlinear ion-acoustic solitary waves in a degenerate plasma such as in superdense white dwarfs.     

Dissipative Diamagnetism—A Case Study for Equilibrium and Nonequilibrium Statistical Mechanics

Using the path integral approach to equilibrium statistical physics the effect of dissipation on Landau diamagnetism is calculated. The calculation clarifies the essential role of the boundary of the container in which the electrons move. Further, the derived result for diamagnetization also matches with the expression obtained from a time-dependent quantum Langevin equation in the asymptotic limit, provided a certain order is maintained in taking limits. This identification then unifies equilibrium and nonequilibrium statistical physics for a phenomenon like diamagnetism, which is inherently quantum and strongly dependent on boundary effects. In addition we have shown that our results are directly connected with fluctuation induced diamagnetic susceptibility of superconducting grains. PACS Number: 03.65.Yz, 05.20.-y, 05.20.Gg, 05.40.-a, 75.20.-g     

Electronic structure of icosahedral alloys: The case of Al65Cu20Os15

Measurements with photoemission spectroscopy in the photon-energy range 35–130 eV have been used to determine the valence band of the stable icosahedral Al₆₅Cu₂₀Os₁₅. Resonant photoemission near the Os 5p 5d and 4f 5d transitions has been employed to show that the feature in the valence band with the maximum intensity at 1.5 (1) eV below the Fermi level is predominantly of the Os 5d character. This has been additionally verified by conducting the photoemission measurements in the constant-initial-state mode and by using the effect of the Cooper minimum in the photoionization cross section of the Os 5d orbitals. The valence band feature with the maximum intensity at 3.7 (1) eV below the Fermi level has been shown as being due mainly to the states of the Cu 3d character. The Os 5d and Cu 3d empirical partial density of states have been determined from the photoemission spectra. The decrease of intensity towards the Fermi level has been interpreted as being indicative of the presence of a theoretically predicted pseudogap around the Fermi level. It has been indicated, however, that the Fermi cut-off also contributes to the observed intensity decrease. It has been demonstrated that the energy resolution of the spectroscopic measurements performed so far on quasicrystals was not high enough to unambiguously determine the presence of such a pseudogap. No unusual features in the valence band of icosahedral Al₆₅Cu₂₀Os₁₅, which could be ascribed to its quasiperiodic nature, have been observed within the resolution of the experiment. High energy-resolution spectroscopic measurements were also shown to be essential to observe the theoretically predicted spikiness of the density of states in quasicrystals. A critical review of published spectroscopic data on the electronic structure of quasicrystals has also been presented.     

Analysis of the diamagnetic effect in multipole Galatea traps

The toroidal current emerging after the injection of a plasmoid through the magnetic shell of the Trimyx-3M (microwave) multipole trap is measured using the Rogowski loop. This current is due to diamagnetism of the plasma. The relation between the diamagnetic current and the maximal plasma pressure produced at the magnetic field separatrix is obtained. It is shown hence that magnetic measurements in a multi-pole trap for a known concentration make it possible to determine the plasma temperature in the trap and the energy confinement time.     

Magnetic properties of electrons in metal-ammonia solutions

A theoretical approach is proposed to describe the concentration and temperature dependence of the static magnetic susceptibility of a metal-ammonia solution. A mechanism is also suggested to explain the transition of the system from the paramagnetic to the diamagnetic state. The theory is based on the assumption that both single-particle and two-electron bound singlet formations of the bipolar type exist in the solution. It is shown that diamagnetism is due to the electron orbital motion and to the relative motion of the quasiparticles. Zh. Tekh. Fiz. 67, 1–13 (August 1997)     

Anomalous magnetism of small metallic clusters in a weak magnetic field

Anomalous diamagnetism in small magnetic fields may be observed in systems consisting of size-quantized metallic clusters. With the increase of magnetic field the diamagnetic susceptibility decreases until ordinary values χ₀ ～ 10^-5 -10^-6. The conditions for the existence of anomalous paramagnetism and orbital ferromagnetism in such systems are also discussed. An increase of the diamagnetic susceptibility in anisotropic semiconductors due to impurities is predicted.     

Magnetization in the ultraquantum limit

The magnetization below and far above the quantum limit for small Fermi surface orbits has been measured in the metallic compound LaRhIn(5). The magnetization due to a pocket of Fermi surface that comprises less than 1 part in 10(4) of the total Brillouin zone volume, and for which the quantum limit is approximately 7 T, leads to the appearance of an overall sample magnetic moment at fields between 7 and 32 T. This moment arises from diamagnetic currents produced by electrons in the ultraquantum limit. A model calculation of the origin and magnitude of the effect is in excellent agreement with the measured field dependence of the induced magnetization.     

Equilibrium spin currents: non-Abelian gauge invariance and color diamagnetism in condensed matter

The spin-orbit (SO) interaction acts on electrons in condensed matter as an effective non-Abelian field. I show that a magnetic component of this field inevitably generates diamagnetic color currents which are just the equilibrium spin currents discussed in a condensed matter context. Since the non-Abelian magnetic field generated by SO coupling is generically nonzero, the equilibrium spin currents are universally present in any physical system, e.g., in molecules or solids with SO interaction. These universal spin currents provide an explicit realization of a non-Abelian Landau diamagnetism.     

The magnetic susceptibility of TMTSF-DMTCNQ under pressure

The susceptibility of TMTSF-DMTCNQ was measured in the newly discovered highly-conducting state under pressure. At a pressure of 12 kbar, the susceptibility χ_m (with the core diamagnetism subtracted) changes sign from the room-temperature paramagnetic value and becomes diamagnetic at a temperature of approximately 30 K. At a temperature of 5–10 K χ_m reaches a value of approximately ?7 × 10^?4 emu mole^?1. This value is about 3 times larger than the previously reported diamagnetism of HMTSF-TCNQ.     

Landau diamagnetism within Tsallis thermostatistics and quantum groups

In this study, using the base of coherent states, Landau diamagnetism has been generalized within Tsallis Thermostatistics. As far as we know, this is the first attempt to introduce coherent states in this formalism. The magnetization and the susceptibility of the system have been obtained and compared with the standard result to illustrate the effect of nonextensivity. Then, adding a perturbation term to the Hamiltonian of the system, nonextensive effects on diamagnetic susceptibility have been investigated. In addition to this, making use of the -deformed partition function of the -oscillator system, the magnetization for -deformed Landau diamagnetism has been derived, with the aim of comparing the results obtained within both formalisms. Received: 21 July 1997 / Revised: 12 December 1997 / Accepted: 23 January 1998     

Correlation between diamagnetic susceptibility and electron spin resonance feature for various multiwalled carbon nanotubes

Determination of the structural features is a fundamental subject in nanotube research. A simple method is proposed to evaluate the structure of multiwalled carbon nanotubes (MWNTs) having either the concentric or the scrolled structure. Although transmission electron microscopy and Raman scattering did not indicate a distinct difference in the structural features of the MWNTs, the temperature dependence of the diamagnetic susceptibility showed a clear difference; one was temperature-independent constant diamagnetism and the others indicated temperature-dependent diamagnetic susceptibilities with different magnitudes. The former phenomenon can be explained by applying the nested concentric nature to the MWNTs, and the latter by the scrolled nature. The difference in the magnitude of the temperature dependence is evidence for the mixed nature of the concentric and scrolled structures. PACS 61.46.Fg; 75.75.+a; 76.30.Pk; 78.67.Ch; 81.07.De     

Texture and magnetic anisotropy of carbon nanotubes in cathode deposits obtained by the electric-arc method

The principal values of the diamagnetic susceptibility of nanotubes are found by comparing the texture parameters of carbon multiwalled nanotubes in cathode deposits with their magnetic anisotropy. It is shown that the susceptibility along the nanotubes is essentially identical to the atomic susceptibility of carbon, and the large average diamagnetism of multiwalled nanotubes is due to the susceptibility component normal to the carbon layers, whose value in the temperature range 4–900 K can be completely explained on the basis of the band model of quasi-two-dimensional graphite. Pis’ma Zh. éksp. Teor. Fiz. 70, No. 7, 468–472 (10 October 1999)     

Spin Polarization and Andreev Conductance through a Diluted Magnetic Semiconductor Quantum Wire with Spin--Orbit Interaction

Spin-dependent Andreev reflection and spin polarization through a diluted magnetic semiconductor quantum wire coupled to normal metallic and superconductor electrodes are investigated using scattering theory. When the spin-orbit coupling is considered, more Andreev conductance steps appear at the same Fermi energy. Magnetic semiconductor quantum wire separates the spin-up and spin-down electrons. The Fermi energy, at which different- spin-state electrons begin to separate, becomes lower due to the effect of the spin-orbit interaction. The spin filter effect can be measured more easily by investigating the Andreev conductance than by investigating the normal conductance.     

Localization and dephasing driven by magnetic fluctuations in low carrier density colossal magnetoresistance materials

Localization and dephasing of conduction electrons in a low carrier density ferromagnet due to scattering on magnetic fluctuations is considered. We claim the existence of the “mobility edge”, which separates the states with fast diffusion and the states with slow diffusion; the latter is determined by the dephasing time. When the “mobility edge” crosses the Fermi energy a large and sharp change of conductivity is observed. The theory provides an explanation for the observed temperature dependence of conductivity in ferromagnetic semiconductors and manganite pyrochlores. Received 17 January 1999 and Received in final form 12 March 1999     

Absence of Cooper-type bound states in three- and few-electron systems

It is shown that the appearance of a fixed-point singularity in the kernel of the two-electron Cooper problem is responsible for the formation of the Cooper pair for an arbitrarily weak attractive interaction between two electrons. This singularity is absent in the problem of three and few superconducting electrons at zero temperature on the full Fermi sea. Consequently, such three- and few-electron systems on the full Fermi sea do not form Cooper-type bound states for an arbitrarily weak attractive pair interaction. Received: 9 February 1998 / Revised and Accepted: 13 May 1998     

Apparent diamagnetism in quasi-two-dimensional Heisenberg antiferromagnets

We observed an apparent diamagnetism in representative quasi-two-dimensional Heisenberg canted antiferromagnets, (C_nH_2n+1NH₃)₂MnCl₄, indicating that the quasi-one-dimensionality is not essential for the apparent diamagnetism. The apparent diamagnetic response seems to be promoted by a thermal quenching and is characterized by a linear response to the applied magnetic field with a constant internal field.     

Diamagnetic susceptibility obtained from the six-vertex model and its implications for the high-temperature diamagnetic state of cuprate superconductors

We study the diamagnetism of the six-vertex model with the arrows as directed bond currents. To our knowledge, this is the first study of the diamagnetism of this model. A special version of this model, called the F model, describes the thermal disordering transition of an orbital antiferromagnet, known as d-density wave, a proposed state for the pseudogap phase of the high-T(c) cuprates. We find that the F model is strongly diamagnetic and the susceptibility may diverge in the high-temperature critical phase with power-law arrow correlations. These results may explain the surprising recent observation of a diverging low-field diamagnetic susceptibility seen in some optimally doped cuprates within the d-density wave model of the pseudogap phase.     

Spectral and thermodynamic properties of electrons in mobility gap states of covalent glasses

Spectral and thermodynamic properties of electrons (holes) in covalent semiconducting glasses are considered in which self-trapping of electron (hole) pairs is realized with negative effective correlation energy U^?. Unlike the Anderson model, electron (hole) pairing is restricted to a small part of the glass bonds. Ranges of the U^? values are found in which either pair effects (suppression of paramagnetism etc.) or single-particle effects predominate; the concentration of the pair states and of the occupied ones can roughly be estimated and can be fairly high. The problem of the coexistence of the Fermi level pinning and effective diamagnetism in glasses is discussed. Some related effects are briefly considered.